Waste water treatment plants may include anaerobic bacterial digesters that are operable to assist in the purification of waste water, which digesters produce a gaseous effluent stream which contains methane, carbon dioxide, entrained water vapor, bacteria, and hydrogen sulfide traces. This effluent gas must be disposed of, and is presently commonly flared. This gaseous product of the digester is presently considered to be a nuisance at best, and a potentially environmental pollutant due to its carbon dioxide, methane and hydrogen sulfide constituents. This gas, however, has the potential to be put to useful purposes if certain of the contaminants, particularly the hydrogen sulfide, were removed therefrom. Hydrogen sulfide can be chemically removed from a gas stream via the Claus reaction (H.sub.2 S+1/2O.sub.2 .fwdarw.H.sub.2 O+S). This reaction cannot be sustained in an anaerobic digester effluent gas stream, however, due to the lack of sufficient oxygen in such a gas stream, since the digestion reaction takes place in an essentially oxygen-free environment in the digester. It would be desirable to devise a system which would readily allow the removal of digester gas contaminants so that the resultant gas stream could be put to a useful purpose, or cleanly disposed of.